阅读说明：本技术 一种基于delta-sigma与PID控制的逆变器及控制方法 (Inverter based on delta-sigma and PID control and control method ) 是由 张宇 鲁博 于 2020-11-25 设计创作，主要内容包括：本发明公开了一种基于delta-sigma与PID控制的逆变器及控制方法,属于开关电源领域,逆变器包括：桥式逆变电路,用于将输入的直流信号转换为交流信号；PID外环控制模块,连接桥式逆变电路的输出端,用于对桥式逆变电路的输出端信号依次进行AD采样、数字PID控制和数模转换处理后输出；delta-sigma内环控制模块,连接桥式逆变电路的桥臂中点和PID外环控制模块的输出端,用于对桥臂中点信号和PID外环控制模块输出信号之间的差值进行delta-sigma调制后输出驱动信号,并根据驱动信号驱动桥式逆变电路的开关管以将直流信号转换为交流信号。delta-sigma内环控制利用其噪声整形原理有效抑制开关电源死区等误差,加入数字式PID控制抑制输出滤波器导致的误差,调节更为灵活,提升电源的精度和稳定性。(The invention discloses an inverter based on delta-sigma and PID control and a control method, belonging to the field of switching power supply, wherein the inverter comprises: the bridge inverter circuit is used for converting an input direct current signal into an alternating current signal; the PID outer ring control module is connected with the output end of the bridge type inverter circuit and is used for outputting the output end signal of the bridge type inverter circuit after AD sampling, digital PID control and digital-to-analog conversion processing are sequentially carried out on the output end signal; and the delta-sigma inner loop control module is connected with the bridge arm midpoint of the bridge inverter circuit and the output end of the PID outer loop control module, and is used for performing delta-sigma modulation on the difference value between the bridge arm midpoint signal and the output signal of the PID outer loop control module, outputting a driving signal and driving a switching tube of the bridge inverter circuit according to the driving signal so as to convert the direct current signal into an alternating current signal. The delta-sigma inner loop control effectively inhibits errors such as dead zones of the switching power supply by utilizing the noise shaping principle of the delta-sigma inner loop control, adds a digital PID control to inhibit errors caused by an output filter, is more flexible to adjust, and improves the precision and the stability of the power supply.)

1. A delta-sigma and PID control based inverter, comprising:

the bridge type inverter circuit (1) is used for converting an input direct current signal into an alternating current signal;

the PID outer ring control module (2) is connected with the output end of the bridge type inverter circuit (1) and is used for outputting the output end signal of the bridge type inverter circuit (1) after AD sampling, digital PID control and digital-to-analog conversion processing are sequentially carried out;

and the delta-sigma inner loop control module (3) is connected with the bridge arm midpoint of the bridge inverter circuit (1) and the output end of the PID outer loop control module (2), and is used for performing delta-sigma modulation on the difference value between the bridge arm midpoint signal and the output signal of the PID outer loop control module (2) and then outputting a driving signal, and driving a switching tube of the bridge inverter circuit (1) according to the driving signal so as to convert the direct current signal into an alternating current signal.

2. The delta-sigma and PID control based inverter according to claim 1, characterized in that the delta-sigma inner loop control module (3) comprises an integrator (31), a comparator (32) and a driving circuit (33);

the integrator (31) is used for integrating the difference value and outputting an integration result to the comparator (32); the comparator (32) is used for comparing the integration result with a preset reference voltage and generating the driving signal; the driving circuit (33) is used for driving a switching tube of the bridge type inverter circuit (1) according to the driving signal.

3. The delta-sigma and PID control based inverter according to claim 2, characterized in that the delta-sigma inner loop control module (3) is a first order control module or a higher order control module.

4. The delta-sigma and PID control based inverter according to claim 2, characterized in that the comparator (32) is a hysteresis comparator or a single limit comparator.

5. The delta-sigma and PID control based inverter according to claim 1, wherein the PID outer loop control module (2) comprises an isolated sampling sub-module (21), a digital PID control sub-module (22), a digital isolation sub-module (23) and a decoding sub-module (24);

the isolation sampling submodule (21) is used for carrying out AD sampling on a signal at the output end of the bridge type inverter circuit (1); the digital PID control sub-module (22) is used for carrying out PID adjustment on a difference value between a sampling result of the isolation sampling sub-module (21) and a preset sinusoidal signal and transmitting a PID adjustment result to the decoding sub-module (24) through the digital isolation sub-module (23); and the decoding submodule (24) is used for performing digital-to-analog conversion on the PID regulation result and outputting the result.

6. The delta-sigma and PID control based inverter according to claim 5, wherein the digital PID control sub-module (22) is an FPGA chip or a DSP chip.

7. The delta-sigma and PID control based inverter according to claim 1, wherein the bridge inverter circuit (1) is a half bridge inverter circuit or a full bridge inverter circuit, an LC filter is connected to an output end of the bridge inverter circuit (1), and the PID outer loop control module (2) is connected to an output end of the LC filter.

8. The delta-sigma and PID control based inverter according to any one of claims 1-7, wherein the delta-sigma inner loop control module (3) controls the switching frequency and duty ratio of the switching tube in the bridge inverter circuit (1) according to the driving signal.

9. A control method of an inverter based on delta-sigma and PID is characterized in that the inverter is a bridge inverter and comprises the following steps:

sequentially performing AD sampling, digital PID control and digital-to-analog conversion on the output end signal of the bridge inverter and then outputting a PID control signal;

and delta-sigma modulating the difference value between the signal of the midpoint of the bridge arm of the bridge inverter and the PID control signal, outputting a driving signal, and driving a switching tube of the bridge inverter according to the driving signal to convert a direct current signal into an alternating current signal.

Technical Field

The invention belongs to the field of switching power supplies, and particularly relates to a delta-sigma and PID control-based inverter and a control method.

Background

The high-precision alternating current power supply has important application in the fields of precision manufacturing, precision measurement and medical treatment. Taking a lithography machine system as an example, a workpiece stage and a mask stage require a power amplifier to realize high-dynamic and high-precision indexes under the condition of outputting large current, wherein the realization of the high-precision index with the nonlinear error less than 0.05 percent is the biggest difficulty. The linear power amplifier of the traditional scheme has low efficiency, and is difficult to realize high power and small volume. The switching power supply can solve this problem, but it is difficult to achieve high accuracy due to a dead-time error of the switching power supply, an error generated by an output filter, and the like. Therefore, how to suppress errors such as dead zones of the switching power supply is a matter of concern to those skilled in the art.

Disclosure of Invention

Aiming at the defects and improvement requirements of the prior art, the invention provides an inverter based on delta-sigma and PID control and a control method thereof, aiming at effectively inhibiting errors such as dead zones of a switching power supply and the like through delta-sigma inner loop control, inhibiting errors caused by an output filter through digital PID control, enabling adjustment to be more flexible and improving the precision and stability of the power supply.

To achieve the above object, according to one aspect of the present invention, there is provided a delta-sigma and PID control-based inverter, comprising: the bridge inverter circuit is used for converting an input direct current signal into an alternating current signal; the PID outer ring control module is connected with the output end of the bridge type inverter circuit and is used for outputting the output end signal of the bridge type inverter circuit after AD sampling, digital PID control and digital-to-analog conversion processing are sequentially carried out on the output end signal; and the delta-sigma inner loop control module is connected with the bridge arm midpoint of the bridge inverter circuit and the output end of the PID outer loop control module, and is used for performing delta-sigma modulation on a difference value between a bridge arm midpoint signal and an output signal of the PID outer loop control module, outputting a driving signal, and driving a switching tube of the bridge inverter circuit according to the driving signal so as to convert the direct current signal into an alternating current signal.

Furthermore, the delta-sigma inner loop control module comprises an integrator, a comparator and a driving circuit; the integrator is used for integrating the difference value and outputting an integration result to the comparator; the comparator is used for comparing the integration result with a preset reference voltage and generating the driving signal; the driving circuit is used for driving a switching tube of the bridge type inverter circuit according to the driving signal.

Furthermore, the delta-sigma inner loop control module is a first-order control module or a high-order control module.

Further, the comparator is a hysteresis comparator or a single limit comparator.

Furthermore, the PID outer ring control module comprises an isolation sampling sub-module, a digital PID control sub-module, a digital isolation sub-module and a decoding sub-module; the isolation sampling submodule is used for carrying out AD sampling on the output end signal of the bridge type inverter circuit; the digital PID control sub-module is used for carrying out PID adjustment on a difference value between a sampling result of the isolation sampling sub-module and a preset sinusoidal signal and transmitting a PID adjustment result to the decoding sub-module through the digital isolation sub-module; and the decoding submodule is used for performing digital-to-analog conversion on the PID regulation result and outputting the result.

Furthermore, the digital PID control sub-module is an FPGA chip or a DSP chip.

Furthermore, the bridge inverter circuit is a half-bridge inverter circuit or a full-bridge inverter circuit, the output end of the bridge inverter circuit is connected with the LC filter, and the PID outer loop control module is connected with the output end of the LC filter.

Furthermore, the delta-sigma inner loop control module controls the switching frequency and the duty ratio of a switching tube in the bridge type inverter circuit according to the driving signal.

According to another aspect of the present invention, there is provided a delta-sigma and PID based inverter control method, wherein the inverter is a bridge inverter, comprising: sequentially performing AD sampling, digital PID control and digital-to-analog conversion on the output end signal of the bridge inverter and then outputting a PID control signal; and delta-sigma modulating the difference value between the signal of the midpoint of the bridge arm of the bridge inverter and the PID control signal, outputting a driving signal, and driving a switching tube of the bridge inverter according to the driving signal to convert a direct current signal into an alternating current signal.

Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained: through delta-sigma inner loop control, errors such as dead zones of the switching power supply are effectively restrained by utilizing the noise shaping principle of the delta-sigma inner loop control, errors caused by an output filter are restrained by adding PID control, better transient performance and steady-state precision can be obtained, the output characteristic can be adjusted more flexibly by digital PID control, and the precision and the stability of the power supply are improved.

Drawings

FIG. 1A is a control block diagram of delta-sigma;

FIG. 1B is a delta-sigma output and error Bode plot;

FIG. 1C is a schematic of delta-sigma noise shaping;

FIG. 2 is a schematic control block diagram of a delta-sigma and PID control based inverter according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a circuit structure corresponding to the control block diagram shown in FIG. 2;

FIG. 4A is a comparison of delta-sigma + PID control and prior art PWM + PID control input transfer function Bode plot;

FIG. 4B is a comparison of delta-sigma + PID control and prior art PWM + PID control output current transfer function Bode plot;

FIG. 4C is a comparison of the delta-sigma + PID control with the prior art PWM + PID control error transfer function Bode plot;

fig. 5 is an experimental waveform diagram of an inverter based on delta-sigma and PID control according to an embodiment of the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

the digital PID controller comprises a bridge inverter circuit 1, a PID outer loop control module 2, an isolation sampling submodule 21, a digital PID control submodule 22, a digital isolation submodule 23, a decoding submodule 24, a delta-sigma inner loop control module 3, an integrator 31, a comparator 32 and a driving circuit 33.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

Fig. 2 is a schematic control block diagram of an inverter based on delta-sigma and proportional-Integral-derivative (PID) control according to an embodiment of the present invention. Referring to fig. 2, the inverter based on delta-sigma and PID control in the present embodiment will be described in detail with reference to fig. 1A to 5.

The inverter based on delta-sigma and PID control comprises a bridge type inverter circuit 1, a PID outer loop control module 2 and a delta-sigma inner loop control module 3. And the PID outer ring control module 2 is connected with the output end of the bridge inverter circuit 1 and is used for outputting the output end signal of the bridge inverter circuit 1 after AD sampling, digital PID control and digital-to-analog conversion processing are sequentially carried out. The delta-sigma inner loop control module 3 is connected with a bridge arm midpoint of the bridge inverter circuit 1 and an output end of the PID outer loop control module 2, and is used for performing delta-sigma modulation on a difference value between a bridge arm midpoint signal and an output signal of the PID outer loop control module 2, outputting a driving signal, and driving a switching tube of the bridge inverter circuit 1 according to the driving signal so as to convert a direct current signal at an input side of the bridge inverter circuit 1 into an alternating current signal and output the alternating current signal.

Control block diagram of delta-sigma as shown in fig. 1A, K represents the integrator gain, and can be set to a large value to ensure good noise shaping effect. e.g. of the type^-sTAnd T represents a delay link, and is used for controlling the output change rate of delta-sigma, namely controlling the switching frequency in the bridge inverter circuit 1. In physical terms, the input x (t) can be approximately regarded as a constant value in a plurality of regulation and control periods, the input value is subtracted from the quantized output value, the subtraction result is integrated by the integrator, the value after integration is guaranteed to fluctuate in a small range, and the pulse equivalent of the input to the output can be realized. From a mathematical point of view, in the control block diagram shown in fig. 1A, the transfer function of the input signal x (t) is:

the transfer function of the error signal x (t) is:

for analyzing the characteristics, the delay time T is set to 10 mus, and the integrator gain K is set to 10⁵This parameter ensures that the switching frequencies are substantially the same, and the bode diagram of this structure is shown in fig. 1B. Referring to fig. 1B, it can be seen that the transfer function of the input signal exhibits a low-pass characteristic, i.e., the input signal is rarely attenuated after being modulated by delta-sigma; the error transfer function exhibits a high-pass filtering property, i.e. it suppresses low-band errors, which is called noise shaping, as shown in fig. 1C.

Therefore, errors such as dead zones of the switching power supply can be effectively inhibited by using a noise shaping principle through delta-sigma inner loop control; however, the delta-sigma control does not consider the filter effect, so that errors caused by the output filter are restrained through PID control, better transient performance and steady-state accuracy can be obtained, and the digital PID control enables adjustment to be more flexible.

According to the embodiment of the invention, the bridge inverter circuit 1 is a half-bridge inverter circuit or a full-bridge inverter circuit. Taking the bridge inverter circuit 1 as an example of a half-bridge inverter circuit, the structure of the half-bridge inverter circuit is shown in fig. 3, in which the half-bridge circuit comprises two switching tubes and a primary side dc voltage-stabilizing capacitor C₂And C₃The inversion function is realized by alternately controlling the on-off of the two switching tubes. The output end of the bridge inverter circuit 1 is connected to an LC filter, and the LC filter is composed of an inductor L and a capacitor C shown in fig. 2 and 3. And the PID outer ring control module 2 is connected with the output end of the LC filter.

According to an embodiment of the invention, the delta-sigma inner loop control module 3 comprises an integrator 31, a comparator 32 and a drive circuit 33. The integrator 31 is configured to integrate the difference value and output the integration result to the comparator 32. The comparator 32 is configured to compare the integration result output from the integrator 31 with a preset reference voltage and generate a driving signal, and output the driving signal to the driving circuit 33. The driving circuit 33 is configured to drive the switching tube of the bridge inverter circuit 1 according to the driving signal, so that the bridge inverter circuit 1 converts the dc signal at the input side into an ac signal.

The integrator 31 may be designed as an ideal integrator or a lossy integrator, and may be a first-order integrator or a high-order integrator, so that the delta-sigma inner loop control module 3 implements corresponding first-order control or high-order control. Comparator 32 is a hysteretic comparator or a single limit comparator.

Taking the integrator 31 composed of an operational amplifier, the comparator being a hysteresis comparator composed of two comparators, a reference source and an SR latch, and the driving circuit 33 being a driving chip as an example, the formed delta-sigma inner loop control module 3 is shown in fig. 3. The control process comprises the following steps: through a resistance R₃Sampling is carried out from the middle point of a bridge arm of the bridge type inverter circuit, signals subjected to analog decoding are subtracted, the subtraction difference value is subjected to integration processing by the integrator and then output to the input end of the hysteresis comparator, the hysteresis comparator compares the integration result with two thresholds High _ ref and Low _ ref of the hysteresis comparator to generate High and Low level signals, and the driving chip controls the switching tube according to the High and Low level signals to realize negative feedback.

According to the embodiment of the invention, the PID outer-loop control module 2 comprises an isolation sampling sub-module 21, a digital PID control sub-module 22, a digital isolation sub-module 23 and a decoding sub-module 24. The isolation sampling submodule 21 is configured to perform AD sampling on the output end signal of the bridge inverter circuit 1. The digital PID control sub-module 22 is configured to perform PID adjustment on a difference between the sampling result of the isolated sampling sub-module 21 and a preset sinusoidal signal, and transmit the PID adjustment result to the decoding sub-module 24 through the digital isolated sub-module 23. The decoding submodule 24 is configured to perform digital-to-analog conversion on the PID adjustment result and output the result. The digital PID control sub-module 22 is an FPGA chip or a DSP chip, and the preset sine signal refers to a digital sine wave in the FPGA chip or the DSP chip. And the PID control and communication are realized by utilizing the FPGA or the DSP.

Taking the example that the isolation sampling sub-module 21 is an AD7405 isolation sampling chip, the digital PID control sub-module 22 is an FPGA control, and the decoding sub-module 24 is a 9038 digital-to-analog conversion chip, the formed PID outer-loop control module 2 is as shown in fig. 3. The control process comprises the following steps: the AD7405 samples output voltage from the output side of the LC filter, utilizes the FPGA to adjust PID control parameters to realize PID control and communication, sends the voltage into a 9038 digital-to-analog conversion chip after isolation to obtain an analog signal, and inputs the analog signal to the input end of a delta-sigma inner loop control module, namely to the integrator 31, so that the output filter can be introduced into feedback control.

According to the embodiment of the invention, the delta-sigma inner loop control module 3 controls the switching frequency and the duty ratio of each switching tube in the bridge inverter circuit 1 according to the driving signal output by the delta-sigma inner loop control module 3, so that the bridge inverter circuit 1 converts the direct current signal at the input side into the alternating current signal.

Fig. 4A-4C are graphs showing the control effect of the delta-sigma + PID control of the present embodiment compared to the prior art PWM + PID control. Referring to fig. 4A, it can be seen that the frequency response of the delta-sigma control input to the output becomes flatter after the PID control is added as in the PWM control; referring to fig. 4B, it can be seen that after the delta-sigma control is added with the PID control as with the PWM, the error of the output current with respect to the output voltage is effectively suppressed, and the resonance spike is eliminated; referring to fig. 4C, it can be seen that the delta-sigma + PID control has no error resonance peak, and has better error suppression performance compared with open loop PWM, PWM + PID, or delta-sigma control; therefore, the delta-sigma + PID control has better error suppression capability than the traditional PWM and PWM + PID control, can better suppress errors and the influence caused by output current compared with the simple delta-sigma control, can also suppress resonance peak caused by a filter, and theoretically can be considered to have the best high-precision potential. Referring to fig. 5, it can be seen that the delta-sigma + PID control in this embodiment can reduce the total harmonic distortion to 0.145%, and has a good control effect.

The invention also provides an inverter control method based on delta-sigma and PID, which is used for controlling a bridge inverter and comprises the following steps: sequentially performing AD sampling, digital PID control and digital-to-analog conversion on the output end signal of the bridge inverter and then outputting a PID control signal; and delta-sigma modulating the difference value between the signal of the midpoint of the bridge arm of the bridge inverter and the PID control signal, outputting a driving signal, and driving a switching tube of the bridge inverter according to the driving signal to convert the direct current signal into an alternating current signal.

In this embodiment, the delta-sigma and PID based inverter control method is the same as the working process and principle of the delta-sigma and PID controlled inverter in the embodiment shown in fig. 1A to 5, and is not described herein again.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.